AVRT5 Advanced Topics





The AVRT5 under the hood.

What’s Inside

The AVRT5 is based on an Atmel AVR ATMEGA64 processor, a 2 Meter transceiver module, a CML FX602D caller-ID chip as the FSK demodulator (but not modulator, I think that’s done by a soft-modem running in the AVR). There is an on-board lithium battery and charger, a serial GPS module, a Bluetooth serial module which provides the SPP serial port emulation protocol, a serial port with a non-standard plug, and an adapter cable to connect the serial port to USB.

Serial Commands

These serial commands are known, and can be sent on the KISS serial channel or over Bluetooth. They use a variation of the ancient Hayes Modem protocol. To send a serial command, first send the carriage-return character (control-M on many terminals). Then send the entire command, followed by another carriage-return. You should see an “OK” reply on the serial interface. You must restart the AVRT5 to see the effect of your command.

AT+CALL=callsign Set the callsign to be transmitted.
AT+FREQ=146.3900 Set the frequency for transmission and reception. There must be 3 digits before the decimal and four after the decimal.
AT+BEEP=1 open|0 off Turn the buzzer on or off. The values must be “1 open” or “0 off”, with both the number and word there!
AT+STAT=message Set the status text. 48 characters maximum.
AT+COMM=message Set the comment text. 48 characters maximum.
AT+ENER=message Set the emergency text. 31 characters maximum.
AT+RX=n Set the receive audio level input to the demodulator. n is one digit in the range of 1 through 9.
AT+TX=n Set the transmit deviation level. n is one digit in the range of 1 through 6.

External Display

Configuration referring to the “UI” is regarding an external serial color LCD display which is sold for the AVRT5 and other AVRT-family TNCs. I haven’t tried this device, and don’t know if the programming is only set for Chinese or if there is an English display available. If you turn on one of the UI features and are trying to use a KISS serial interface, this will cause garbage characters to be written to the serial port.

Hardware Modifications

Hardware modifications may be necessary to enable power on/off with USB power and high-altitude mode. These are documented in an instruction by Mark Cheavens KC5EVE.

Custom Programming

The AVR processor comes with a standard serial boot-loader burned into its ROM. The manufacturer’s firmware is delivered as a standard Intel hex file, and is not encrypted, so you can disassemble it with appropriate tools. To load a program (or the manufacturer’s firmware) to the AVRT5 using the standard AVR serial firmware installation utilities, or the Open Source tools, use the serial to USB adapter cable. Turn off the AVRT5, then turn it on and keep holding down the power button during the entire programming process.

Since it is possible to program this device using the standard AVR firmware loader and standard AVR development tools, you can replace the firmware. You can also patch the manufacturer’s firmware. The present manufacturer firmware is so large that there is no space left for other features, so if you attempt this your first task might be removing features, or at least optimizing the space usage of the device.